[sdiy] Dr. Bob speaks on the 904A

[jh.]

> Q: Were the stock 904As supposed to self-resonate?
> A: Well, sure (laughs).
>
> Q: I looked at 6 904As. 3 oscillate and 3 don't. So I wasn't sure.
> A: What can I say.......(laughs).
>
> Q: Do you thinks it's a reduction in loop gain due to aging in the
2N3392s?
> A: (pause)...Something like that.
>
> Q: Does the Voyager self-resonate?
> A: Sure.
>
> Q: The 904As are designed not to resonate below about A440. What about the
Voyager?
> A:It has a much wider range. I learned a lot in 30yrs what people expect.

This makes perfect sense. (;->)
It's not uncommon that a great inventor moves on to more perfection, but the
old original behaviour has its followers. I for one love the frequency
dependent resonance a lot.
Especially since we have a lot of other filters with constant resonance.
One thing is sure: 30 years ago it was difficult to achieve constant
resonance, while today, with BiFet opamps, it's much easier (and less
expensive) to make a constant resonance ladder filter, than to re-create the
behaviour of the vintage filter that started it all.

JH.